The Viking mission was the only mission to date that conducted life detection experiments. It revealed ambiguous and
still controversial results. New findings and hypotheses urge a re-evaluation of the Viking results and a re-evaluation of
the evidence for the possible presence of life on Mars in general. Recent findings of abundant water ice on Mars, the
presence of liquid contemporary water on the Martian surface, and the detection of methane in the Martian atmosphere
further support this possibility. Current missions to be launched focus on habitability considerations (e.g., NASA Phoenix,
NASA Mars Science Laboratory), but shy away from directly testing for life on Mars, with the potential exception of the
ESA ExoMars mission. If these currently planned missions collect positive evidence toward habitability and the possible
existence of extraterrestrial (microbial) life on Mars, it would be timely to propose a new mission to Mars with a strong life
detection component. We propose such a mission called BOLD: Biological Oxidant and Life Detection Mission. The
BOLD mission objective would be to quantify the amount of hydrogen peroxide existing in the Martian soil and to test
for processes typically associated with life. Six landing packages are projected to land on Mars that include a limited
power supply, a set of oxidant and life detection experiments, and a transmitter, which is able to transmit information via
an existing Mars orbiter back to Earth.
The conditions on Mars imply an evolutionary advantage for organisms employing a mixture of H2O2 and H2O in their
intracellular fluid: the H2O2-H2O eutectic freezes at -56.5°C, is hygroscopic and a source of oxygen. Contrary to common
belief, H2O2 is used for a variety of purposes in terrestrial biochemistry. The Viking Lander Biology Experiments have often
been interpreted as the result of inorganic oxidants in the Martian soil. Here, we interpret the Viking findings as the result of
the reactions of H2O2-H2O based life. Several hitherto puzzling findings are explained by the H2O2-H2O hypothesis. The
lack of detected organics is the result of autooxidation of the organisms as these were gradually heated. Supportive
observations were made in the PR and LR experiments. Our interpretation is that the addition of water vapor at a relatively
high temperature could only be withstood by the organisms for a short time, as they perished due to hyperhydration. The
evolution of oxygen in the GEx experiment is explained by the high oxidative content of the organisms as they perished in
this experiment. The PR experimental conditions were most Mars-like and carbon assimilation could be detected but no
growth. Particularly, the GEx experiment allows the calculation of biomass in the Martian soil based on measured evolution
of reaction products. Further properties of the suggested organisms such as metabolic reactions and by-products may be
detected by future Mars missions.
Conference Committee Involvement (1)
Instruments, Methods, and Missions for Astrobiology XI
12 August 2008 | San Diego, California, United States
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